The invention relates to a gas filter device for filtering contaminants (e.g. odorous substances) out of gases, e.g. to be used to neutralize odors from gases arising in sewage treatment engineering or other processes.
Gas filter devices usually have a filter unit; gases to be filtered flow through the filter unit and are filtered in the process. A filter unit of this type can filter solids out of a gas flow, for instance via mechanical actions. Furthermore, a filter unit of that type can bind to a substantial amount of noxious gases via absorption or adsorption until its capacity is exhausted with regard to that and a break-out of noxious gases comes about. There can be provisions, for instance, for the components that are to be removed from the gas flow to be “washed” or “stripped” (with vapor instead of liquid) via a suitable liquid in the absorption phase. As a different example, the constituent parts of the components to be removed can be selectively bound—usually in piles of granulate (e.g. molecular sieves or activated charcoal) or via mats to which an adsorbent is applied. Physical and chemical binding forces are the decisive parameters in the process; the effectiveness of the bonds are dependent, for example, on the gas temperature, the gas moisture content and the pressure. Biological components (e.g. microorganisms) can be added or can form during absorption and also during adsorption. That can lead so far in the process that the biological components provide the decisive forces and dominate the physical or chemical processes. The filter unit can be designed in the form of a biological filter unit, for instance; microorganisms (e.g. fungi or bacteria) use materials that are to be filtered out and that are contained in the gas stream as a nutrient—i.e. they metabolize them—and break them down in the process. The filter unit has a limited filtering capacity. Since a replacement of the used filter unit by an unused filter unit is appropriate as soon as the used filter unit has lost its filtering effect in a position (even if a filtering effect still exists in other positions), an even contaminant load across the filter unit and even filtering activity or an even filtering rate across the filter unit with an even distribution of the contaminants in the gases that are to be filtered out is advantageous for utilization of this filtering capacity that is as complete as possible.